The present invention relates to a circuit an method for reading out picture data written in a main memory and displaying the data on a picture display in an electronic still camera, and more particularly to a multi-picture control circuit and method for accessing pictures written in a main memory and displaying them individually or in groups of more than one at a time.
Generally, in an electronic still camera, a video signal photoelectrically converted by a photoelectric converting device such as a charge-coupled device (CCD), is converted to digital video data by an analog to digital (A/D) converter and is written on a writing medium by frames. The video data written on a writing medium may be erased for other video data or may be stored in another writing medium. A buffer memory performs the former function and a main memory performs the latter function. To write/store a lot of video data, a capacity of main memory is usually set to be far greater than the buffer memory capacity. The video data written in a main memory may be processed by a data processor such as a microcomputer and may be provided for another object such as copying, transmission or reproduction. To see the contents of video data written in a main memory, the video data copied in another buffer memory (buffer memory for reproduction), is sequentially read out, converted to an analog composite video signal by a digital-to-analog (D/A) converter, and displayed on a display apparatus such as a monitor incorporated in an electronic still camera.
FIG. 1 is a block diagram of a circuit for displaying pictures written in a conventional electronic still camera. A video signal from a video input portion 1 is converted to digital video data in an A/D converter 2 and is written by frames in a buffer memory 3. Video data written in the buffer memory 3 may be erased to allow for the writing of additional data in the buffer memory 3, or may be stored in a main memory 4. Main memory 4 can store more than one picture's worth of data. For efficient control of written picture data, each picture's worth of data is written in a page whose writing region is the same as or greater than a writing region for writing one picture of data. Thus, different pages have different pictures of data. In other words, a microcomputer can control written video data by pages regardless of the contents. FIG. 2 illustrates the address designation of pictures of data in the main memory 4 of FIG. 1. Here, the size of one frame is 256 bytes.times.256 bytes and the number of pages is 16. The picture data for one page is divided into horizontal and vertical components. The horizontal component corresponds to horizontal addresses of the picture data and the vertical component corresponds to vertical addresses thereof. For better resolution, through the use of one field capacity by nonsequential scanning, the size of one frame can be 512 bytes.times.512 bytes. If a main memory with this capacity is used, the number of pages becomes 4. Picture data written in each region of main memory 4 can be checked via a picture display 7 of FIG. 1, erased for writing another picture, or moved to another region in main memory. Microcomputer 9 controls main memory 4. To check the written picture data via the picture display, a page is selected from among pages of main memory 4 to read out picture data from the selected page, and writes the read out picture data into a reproducing frame buffer. Picture data written in reproducing buffer memory 5 is read out, corresponding to horizontal and vertical periods suitable for picture display 7, then is converted to analog data by D/A converter 6 to be displayed on picture display 7. Since the picture data written in main memory 4 is read out by pages and written in reproducing buffer memory 5, the conventional electronic still camera is disadvantageous in that the above operation must be repeated as required, or a certain picture region must be particularly designated, in order for a user to see more than one picture.